The present invention relates to fusion molecules composed of mutants or variants of human interleukin-3 (hIL-3) fused to a second colony stimulating factor (CSF) including cytokine, lymphokine, interleukin, hematopoietic growth factor or IL-3 variant with or without a linker
Colony stimulating factors (CSFs) which stimulate the differentiation and/or proliferation of bone marrow cells have generated much interest because of their therapeutic potential for restoring depressed levels of hematopoietic stem cell-derived cells. CSFs in both human and murine systems have been identified and distinguished according to their activities. For example, granulocyte-CSF (G-CSF) and macrophage-CSF (M-CSF) stimulate the in vitro formation of neutrophilic granulocyte and macrophage colonies, respectively while GM-CSF and interleukin-3 (IL-3) have broader activities and stimulate the formation of both macrophage, neutrophilic and eosinophilic granulocyte colonies. IL-3 also stimulates the formation of mast, megakaryocyte and pure and mixed erythroid colonies.
Because of its ability to stimulate the proliferation of a number of different cell types and to support the growth and proliferation of progenitor cells, IL-3 has potential for therapeutic use in restoring hematopoietic cells to normal amounts in those cases where the number of cells has been reduced due to diseases or to therapeutic treatments such as radiation and/or chemotherapy.
Interleukin-3 (IL-3) is a hematopoietic growth factor which has the property of being able to promote the survival, growth and differentiation of hematopoietic cells. Among the biological properties of IL-3 are the ability (a) to support the growth and differentiation of progenitor cells committed to all, or virtually all, blood cell lineages; (b) to interact with early multipotential stem cells; (c) to sustain the growth of pluripotent precursor cells; (d) to stimulate proliferation of chronic myelogenous leukemia (CML) cells; (e) to stimulate proliferation of mast cells, eosinophils and basophils; (f) to stimulate DNA synthesis by human acute myelogenous leukemia (AML) cells; (g) to prime cells for production of leukotrienes and histamines; (h) to induce leukocyte chemotaxis; and (i) to induce cell surface molecules needed for leukocyte adhesion.
Mature human interleukin-3 (hIL-3) consists of 133 amino acids. It has one disulfide bridge and two potential glycosylation sites (Yang, et al., CELL 47:3 (1986)).
Murine IL-3 (mIL-3) was first identified by Ihle, et al., J. IMMUNOL. 126:2184 (1981) as a factor which induced expression of a T cell associated enzyme, 20-hydroxysteroid dehydrogenase. The factor was purified to homogeneity and shown to regulate the growth and differentiation of numerous subclasses of early hematopoietic and lymphoid progenitor cells.
In 1984, cDNA clones coding for murine IL-3 were isolated (Fung, et al., NATURE 307:233 (1984) and Yokota, et al., PROC. NATL. ACAD. SCI. USA 81:1070 (1984)). The murine DNA sequence coded for a polypeptide of 166 amino acids including a putative signal peptide.
The gibbon IL-3 sequence was obtained using a gibbon cDNA expression library. The gibbon IL-3 sequence was then used as a probe against a human genomic library to obtain a human IL-3 sequence.
Gibbon and human genomic DNA homologues of the murine IL-3 sequence were disclosed by Yang, et al., CELL 47:3 (1986). The human sequence reported by Yang, et al. included a serine residue at position 8 of the mature protein sequence. Following this finding, others reported isolation of Pro8 hIL-3 cDNAs having proline at position 8 of the protein sequence. Thus it appears that there may be two allelic forms of hIL-3.
Dorssers, et al., GENE 55:115 (1987), found a clone from a human cDNA library which hybridized with mIL-3. This hybridization was the result of the high degree of homology between the 3xe2x80x2 noncoding regions of mIL-3 and hIL-3. This cDNA coded for an hIL-3 (Pro8) sequence.
U.S. Pat. Nos. 4,877,729 and 4,959,454 disclose human IL-3 and gibbon IL-3 cDNAs and the protein sequences for which they code. The hIL-3 disclosed has serine rather than proline at position 8 in the protein sequence.
Clark-Lewis, et al., SCIENCE 231:134 (1986) performed a functional analysis of murine IL-3 analogs synthesized with an automated peptide synthesizer. The authors concluded that the stable tertiary structure of the complete molecule was required for full activity. A study on the role of the disulfide bridges showed that replacement of all four cysteines by alanine gave a molecule with {fraction (1/500)}th the activity as the native molecule. Replacement of two of the four Cys residues by Ala(Cys79, Cys140xe2x86x92Ala79, Ala140) resulted in an increased activity. The authors concluded that in murine IL-3 a single disulfide bridge is required between cysteines 17 and 80 to get biological activity that approximates physiological levels and that this structure probably stabilizes the tertiary structure of the protein to give a conformation that is optimal for function. (Clark-Lewis, et al., PROC. NATL. ACAD. SCI. USA 85:7897 (1988)).
International Patent Application (PCT) WO 88/00598 discloses gibbon- and human-like IL-3. The hIL-3 contains a Ser8xe2x86x92Pro8 replacement. Suggestions are made to replace Cys by Ser, thereby breaking the disulfide bridge, and to replace one or more amino acids at the glycosylation sites.
EP-A-0275598 (WO 88/04691) illustrates that Ala1 can be deleted while retaining biological activity. Some mutant hIL-3 sequences are provided, e.g., two double mutants, Ala1xe2x86x92Asp1, Trp13xe2x86x92Arg13 (pGB/IL-302) and Ala1xe2x86x92Asp1, Met3xe2x86x92Thr3 (pGB/IL-304) and one triple mutant Ala1xe2x86x92Asp1, Leu9xe2x86x92Pro9, Trp13xe2x86x92Arg13 (pGB/IL-303).
WO 88/05469 describes how deglycosylation mutants can be obtained and suggests mutants of Arg54Arg55 and Arg108Arg109Lys110 might avoid proteolysis upon expression in Saccharomyces cerevisiae by KEX2 protease. No mutated proteins are disclosed. Glycosylation and the KEX2 protease activity are only important, in this context, upon expression in yeast.
WO 88/06161 mentions various mutants which theoretically may be conformationally and antigenically neutral. The only actually performed mutations are Met2xe2x86x92Ile2 and Ile131xe2x86x92Leu131. It is not disclosed whether the contemplated neutralities were obtained for these two mutations.
WO 91/00350 discloses nonglycosylated hIL-3 analog proteins, for example, hIL-3 (Pro8Asp15Asp70), Met3 rhuIl-3 (Pro8Asp15Asp70); Thr4 rhuIL-3 (Pro8Asp15Asp70) and Thr6 rhuIL-3 (Pro8Asp15Asp70). It is said that these protein compositions do not exhibit certain adverse side effects associated with native hIL-3 such as urticaria resulting from infiltration of mast cells and lymphocytes into the dermis. The disclosed analog hIL-3 proteins may have N termini at Met3, Thr4, or Thr6.
WO 91/12874 discloses cysteine added variants (CAVs) of IL-3 which have at least one Cys residue substituted for a naturally occurring amino acid residue.
U.S. Pat. No. 4,810,643 discloses the DNA sequence encoding human G-CSF.
WO 91/02754 discloses a fusion protein composed of GM-CSF and IL-3 which has increased biological activity compared to GM-CSF or IL-3 alone. Also disclosed are nonglycosylated IL-3 and GM-CSF analog proteins as components of the fusion.
WO 92/04455 discloses fusion proteins composed of IL-3 fused to a lymphokine selected from the group consisting of IL-3, IL-6, IL-7, IL-9, IL-11, EPO and G-CSF.
The present invention encompasses recombinant human interleukin-3 (hIL-3) variant or mutant proteins (muteins) fused to a second colony stimulating factor (CSF) include, cytokine, lymphokine, interleukin, hematopoietic growth factor (herein collectively referred to as xe2x80x9ccolony stimulating factorsxe2x80x9d) or IL-3 variant with or without a linker. These hIL-3 muteins contain amino acid substitutions and may also have amino acid deletions at either/or both the N- and C-termini. This invention encompasses mixed function colony stimulating factors formed from covalently linked polypeptides, each of which may act through a different and specific cell receptor to initiate complementary biological activities.
Novel compounds of this invention are represented by the formulas
R1-L-R2, R2-L-R1, R1-R2, R2-R1, R1-L-R1 and R1-R1
where R1 is a hIL-3 variant which contains multiple amino acid substitutions and which may have portions of the hIL-3 molecule deleted, R2 is an Il-3, Il-3 variant or CSF with a different but complementary activity. The R1 polypeptide is fused either directly or through a linker segment to the R2 polypeptide. Thus L represents a chemical bond or polypeptide segment to which both R1 and R2 are fused. Preferably, these mutant IL-3 polypeptides of the present invention contain four or more amino acids which differ from the amino acids found at the corresponding positions in the native hIL-3 polypeptide. The invention also relates to pharmaceutical compositions containing the fusion molecules, DNA coding for the fusion molecules, and methods for using the fusion molecules. Additionally, the present invention relates to recombinant expression vectors comprising nucleotide sequences encoding the hIL-3 fusion molecules, related microbial expression systems, and processes for making the fusion molecules using the microbial expression systems.
These fusion molecules may be characterized by having the usual activity of both of the peptides forming the fusion molecule or it may be further characterized by having a biological or physiological activity greater than simply the additive function of the presence of IL-3 or the second colony stimulating factor alone. The fusion molecule may also unexpectedly provide an enhanced effect on the activity or an activity different from that expected by the presence of IL-3 or the second colony stimulating factor or IL-3 variant. The fusion molecule may also have an improved activity profile which may include reduction of undesirable biological activities associated with native hIL-3.
The present invention also includes mutants of hIL-3 in which from 1 to 14 amino acids have been deleted from the N-terminus and/or from 1 to 15 amino acids have been deleted from the C-terminus, containing multiple amino acid substitutions, to which a second colony stimulating factor or IL-3 variant has been fused. Preferred fusion molecules of the present invention are composed of hIL-3 variants in which amino acids 1 to 14 have been deleted from the N-terminus, amino acids 126 to 133 have been deleted from the C-terminus, and contains from about four to about twenty-six amino acid substitutions in the polypeptide sequence fused to second colony stimulating factor or IL-3 variant.
The present invention also provides fusion molecules which may function as IL-3 antagonists or as discrete antigenic fragments for the production of antibodies useful in immunoassay and immunotherapy protocols.
Antagonists of hIL-3 would be particularly useful in blocking the growth of certain cancer cells like AML, CML and certain types of B lymphoid cancers. Other conditions where antagonists would be useful include those in which certain blood cells are produced at abnormally high numbers or are being activated by endogenous ligands. Antagonists would effectively compete for ligands, presumably naturally occurring hemopoietins including and not limited to IL-3, GM-CSF and IL-5, which might trigger or augment the growth of cancer cells by virtue of their ability to bind to the IL-3 receptor complex while intrinsic activation properties of the ligand are diminished. IL-3, GM-CSF and/or IL-5 also play a role in certain asthmatic responses. An antagonist of the IL-3 receptor may have the utility in this disease by blocking receptor-mediated activation and recruitment of inflammatory cells.
In addition to the use of the fusion molecules of the present invention in vivo, it is envisioned that in vitro uses would include the ability to stimulate bone marrow and blood cell activation and growth before infusion into patients.